To flourish in a microbe-rich world, higher eukaryotic organisms have evolved sophisticated signaling, metabolic, and structural pathways configured to promote beneficial microbiomes, while simultaneously resisting pathogen attack. Millions of years of co-evolution between hosts and microbes have resulted in a fascinating world of attack, counter-attack, deception, and hijacking mechanisms, all of which are essential to our understanding of life on Earth. In our lab, we probe these intricate host-microbe interactions primarily using a model system consisting of the plant Arabidopsis thaliana, its microbiome, and the bacterial pathogen Pseudomonas syringae.

Our research is designed to answer the following fundamental questions:

1) How do microbial pathogens attack and infect host plant?

2) How do environmental factors impact bacterial pathogenesis?

3) How do plants select and maintain beneficial microbiomes?

We strive to build the knowledge necessary to develop long-term solutions to promote plant health and global food security, including a new generation of climate-resilient “dream” plants.

I. Mechanisms of Bacterial Pathogenesis

Over the years, we have studied how the bacterial pathogen P. syringae infects Arabidopsis thaliana. We have elucidated the molecular actions of several bacterial virulence proteins (called effector proteins) and a toxin called coronatine, which structurally mimics the plant hormone jasmonate. We are continuing this area of research to further our understanding of how bacterial pathogens manipulate host stomata, immune responses, and apoplast microenvironment during the course of infection. This line of research is not only relevant to understanding the molecular basis of numerous plant diseases, but also provides conceptual parallels to the study of bacterial pathogenesis in animals and humans.

II. Environment and Disease Susceptibility

A long-standing dogma in plant disease susceptibility states that disease development requires not only the presence of a virulent pathogen and a susceptible host, but also a set of disease-favoring environmental conditions. How environment conditions influence the plant and the pathogen during an active interaction is poorly understood, leaving a big gap in our understanding of how disease outbreaks occur in nature. To gain insight into the molecular basis of the “disease triangle” dogma, we initiated a project aimed at elucidating how two prominent abiotic environmental factors (temperature and humidity) intercept the molecular network associated with disease development.

III. Plant Microbiome and Disease Susceptibility

Current studies of disease susceptibility in plants have largely ignored the potential effects of the indigenous microbiome present on each plant. Anticipating that the next phase of research on disease susceptibility needs to consider the microbiome as an integral component of a multi-dimensional interaction during disease development, we initiated a project to develop soil-based gnotobiotic plant growth systems (called “FlowPot” and “GnotoPot”). Similar to the “germ-free mouse” gnotobiotic system for medical research, we anticipate that the FlowPot and GnotoPot systems will enable plant scientists to study the role of the microbiome in modulating various aspects of plant biology, including the phenomenon of microbial dysbiosis in the plant kingdom.